4140:

Disclaimer:The content of this page is for general information only and is not to be used for engineering or design. The content of this material specification page was compiled from available public sources and authorities on material properties. Although we believe the information to be corrrect, Metal Stock, Inc. is not responsible for the accuracy of any of the material specifications and only presents this data as general information for our customers.

4140 is a chromium-molybdenun alloy steel that can be oil hardened to relatively high hardenability. The chromium content provides good hardness penetration, and the molybdenum imparts uniformity of hardness and high strength. Through variations in the method of heat treating 4140, an exceptionally wide range of properties can be attained. For this reason, it is often used as stock for forging, as 4140 has self scaling properties. 4140 responds readily to heat treatment and is comparatively easy to machine in the heat treated condition. 4140 resists creep in temperatures up to 1000° F and maintains its properties even after long exposure at these relatively high working temperatures. Other desirable properties include good wear resistance, excellent toughness, and good ductility in the quenched and tempered condition. 4140 cold finished annealed is available in rounds, squares, rectangles, and hexagons. 4140 cold rolled rounds is also available with an addition of .15-.35 lead (41L40), which improves machinability (77% of 1212, surface cutting speed 127 ft/min) without sacrificing other desirable properties, with the exception that the use of 41L40 is not recommended for applications above 400°F, since at elevated temperatures, ductility in 41L40 is low.

4140 has a machinability rating at 66% of B1112. Average cutting speed is 110 ft/min. 4140 is difficult to weld, but can be welded by any of the common welding practices providing section is preheated and stress relieved after welding. 4140 is not recommended due to the fumes produced with the addition of lead.

HEAT TREATING - Forging, Normalizing, and Annealing:

HEAT TREATING:
4140 has a hardening range of 1525° - 1625° F. Quench in oil. A wide range of mechanical properties can be obtained by tempering between 400° and 1300° F.